CHAPTER VI. 



OTHER USEFUL MINERALS AND ORES. 



Black lead. Coal ; anthracite ; bituminous ; brown coal. Bitumen , 

 asphalt; naphtha; petroleum. Gypsum. Apatite. Alum. 

 Borax Common salt ; nitrate of soda ; phosphate of lime ; heavy 

 spar ; fluor-spar ; carbonate of lime. Precious stones and gems ; 

 diamond. Table of characteristics of various precious stones and 

 gems. 



GRAPHITE (Hack lead}. 



Lustre metallic. 

 Colour dark steel grey. 

 Streak black and shining 

 H. 1-2; S.G. 2-1. 



Is greasy to the touch. Soils paper, if rubbed on it 

 Contains about 90 per cent, carbon ; the rest, iron, lime, &c. 

 Is infusible before the blowpipe and insoluble in acids. In 

 Cumberland, England, blacklead-bearing strata are found 

 in slate rocks interbedded with trappean rocks. In Ceylon, 

 in the upper strata of Devonian formation. In the United 

 States of America, gneissic rock. Graphite is used in the 

 manufacture of lead pencils, crucibles, &c. 



COAL. 



True coal (not lignite and brown coal) is usually found in 

 beds or seams divided from one another by beds of shale, 

 sandstone, grit, and clay, in the Coal measures belonging to 

 the Carboniferous formation. The principal varieties are 



Anthracite. 



A black, shining coal with sharp edges and conchoidal 

 fracture. Streak, black. Does not soil the fingers. Is 

 not easily lighted, but when alight gives out an intense 



